# Partial-Output Salvage > Stream every model token to an atomic partial file so mid-stream crashes leave a consistent salvage — then surface the recovery status to the model on the next prompt. - **Category**: Agentic AI - **Subcategory**: Cognition & Introspection - **Canonical URL**: https://designpattern.fyi/patterns/partial_output_salvage/ --- ## Description **Intent**: Without a partial-output mechanism, a SIGKILL mid-inference loses all tokens that were streaming — minutes of model time and real context gone with no trace. **Context**: The agent runs on hardware that occasionally crashes: OOM killer, watchdog timer, deploy restart mid-stream. Per-call inference is long enough that losing a half-finished stream is meaningful. The existing resumption pattern only restores durably written state — not the tokens that were streaming when the kill signal landed. **Solution**: Mechanical finite-state machine. On stream start: open partial.tmp, write a start marker with thought-id, timestamp, model ID. On each chunk: append to tmp, periodically os.rename(tmp, partial) for atomicity. On normal stream end: rename to canonical thought path, delete partial. On startup: scan for orphan partial.* files, finalize each with a typed RecoveryStatus enum (RECOVERED_FROM_PARTIAL for hard kill, TIMEOUT_PARTIAL for watchdog timeout). Include last_partial_recovery: in the next prompt's system context so the model can adjust. ## Use Cases - The runtime can SIGKILL the agent mid-stream and that loses meaningful work. - Inference is long enough per call that a partial stream has real salvage value. - The filesystem supports atomic rename in the working directory. ## Trade-offs ### Advantages - Mid-stream tokens are not lost on hard crash — minutes of inference are recoverable - Typed recovery marker preserves debuggability — the salvage isn't hidden from the model - Atomic rename keeps the partial file readable and consistent at every moment ### Considerations & Drawbacks - Rename overhead per N chunks is non-zero; chunk size needs tuning - Partials add filesystem clutter if not periodically cleaned up - Recovery status surfaced in the prompt costs tokens every time it fires --- **Reference**: [Original Source](https://www.agentpatternscatalog.org/patterns/partial-output-salvage/)